Evidence syntheses in child health.

Evidence syntheses, also known as systematic reviews, differ from traditional reviews in that they are scientific evaluations of existing studies. Systematic reviews have explicit and reproducible methods and, as with any other scientific endeavor, the result of an evidence synthesis or systematic review can be critically appraised. Many sources for high-quality evidence syntheses now exist, with considerable support from government agencies to develop both the methods and the products of such reviews. Evidence syntheses can increase the efficiency and effectiveness of medical practice but face many hurdles, particularly in child health. These center around 4 areas: lack of high-quality primary studies, the difficulty of finding studies that do exist, the variability and usefulness of the outcome measures in child health, and problems with production and dissemination. Increasing attention to the need for high-quality child health research will help to ameliorate some of these issues, whereas solutions to others are under development or remain elusive.